Accurate dark matter halo elongation from weak-lensing stacking analysis

Halo shape estimates that describe their anisotropic mass distribution are valuable parameters that provide useful information on their assembly process and evolution. Measurements of the mean shape estimates for a sample of cluster-size halos, can be used to test halo formation scenarios as well as improving the modelling of potential biases in constraining cosmological parameters using these systems. In this work we test the recovery of halo cluster shapes and masses applying weak lensing stacking techniques, using lensing shear and a new dark matter halo catalogues, derived from the light-cone output of the cosmological simulation MICE-GC. We perform this study by combining the lensing signals obtained for several samples of halos selected according to their mass and redshift, considering the main directions of the dark-matter distributions. In the analysis we test the impact of several potential introduced systematics, such as the adopted modelling, the contribution of the neighbouring mass distribution, miscentering and misalignment effects. Our results show that, when some considerations regarding the halo relaxation state are taken into account, the lensing semi-axis ratio estimates are in agreement within a $5\%$ with the mean shapes of the projected dark-matter particle distribution of the stacked halos. The presented methodology provides a useful tool to derive reliable shapes of galaxy clusters and to contrast them with those expected from numerical simulations. Furthermore, our proposed modelling, that takes into account the contribution of neighbouring halos, allows to constraint the elongation of the surrounding mass distribution.Comment: 15 pages, 8 figures, submitted to MNRA